I'm ADD to the core, and I find it actually easier to zone out and code with a low-level background noise, "coffee-shop" style. Large spikes in noise are a problem, and also non-relevant conversations that pull everyone's attention off-task, but on the open teams I've been on, in general this has been the exception not the rule.

My experience at large tables has been that good coders and PMs will actually IM a developer when they need to ask a question -- I do this all the time even when I'm sitting 2 feet from the guy I need to talk to: "let me know when you have a sec to talk about X", etc.

Again, that's evidence of a team that's generally on-task and communicating well -- a cultural quality that is itself harder to find than not.